Drying finely-divided materials



H. F. CHAPPELL.

DRYING FINELY DIVIDED MATERIAL APPLICATION FILED NOV. 14. 1918. 1,375,080. P ented Apr- 19, 1921.

3 SHEETS-SHEET 1.

H. F. CHAPPELL.

DRYING FINELY DIVIDED MATERIALS.

APPLICATION FILED NOV. I4| 191B. 1,37 5,080. Patented Apr- 19, 1921. v

3 SHEETS-SHEET 2.

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WI M H. F. CHAPPELL.

DRYING FINELY DIVIDED MATERIALS.

APPLICATION FILED NOV. I4. 1918.

1,375,080, Patented Apr. 19, 1921 3 SHEETS-SHEET 3.

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- MM aw E'EED STATES PATENT f) HOWARD CHAPPELL, OF NEW YORK, N. Y. Y

' DRYING rmrinY-nIvInEn MATERIALS.

To all whom it camera:

Be it known that I HOWARD F. CHAP- rm, a'citizen of the llnited States, residmg at New York, in the county of New York, Stateof New York, have invented certain new and useful Improvements in' Drying Finely-Divided Materials; and I do hereby declare the followingto be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains tomake and use the same. x

This invention relates to the drying of finely-divided materials, such as fine graphite, fine concentrates, and more particularlythe fine material discharged as filter cake from vacuum and pressure filters, and the like. One of the principal uses of the in vention consists, for instance, in the drying of the filter cake discharged from a filter press of the well-known Kelly type in the treatment of finely-divided leached calcined alunite.

Materials of this general character, and

especially leached calcined alunite (alumlna) .filter cake, are frequently so fine that after they have parted with a consider-- able part out their moisture a relatively slight draft of air will carry away a notable amount of the material. Accordingly, serious losses accompany the drying of such materials in the usual types of so-called direct-heating apparatus relying upon a circulation of heated air, products of combustion, or the like, over and in contact with the charge; and, even where means are employed, suchas a cyclone dust collector, for recovering, as far as it is feaslble to do so, the material carried away from the charge, such recovery is accompanied in large part with re-condensation of the moisture, so that the recovered material must be returned to the drier. The employment of stirring devices in these direct drlers magnifies their dust-producing characteristics to such a degree as to ren er them wholly impracticable for economical service for the treatment of these extremely finely-divided materials.

tivity for heat makes it diflicult and expensive to continue, the drying operation to ad- Specification of Letters Patent.

Patented Apr. 19, 1921.

Application filed November 14, 1918. Serial N10. 262,450.

vantage as soon as a bottom layer of comparatively moderate depth of dry material has formed.

The present invention has for its object not only to provide an efiicient drier for these finely-divided materials, avoiding the dust losses referred to, but also 'to speed up the drying operation by utilizing to special advantage the products of combustion or other heating medium, and to make the operation continuous and readily regulable by the operator, who can at all times observe its progress and can regulate its conditions to suit the requirements of the charge, the desired or predetermined output. per unit of time, and the degree of dehydration contemplated.

.To this end, the inventionprovides an apparatus wherein the charge may be fed continuously, at a rate to be determined by the operator, and may be spread out at a regulable depth upon a heated endles traveling platform. he platform, as will hereinafter more fully appear consists'of a series of plates or pans, assembled to form the The upper strand of the traveling plat-- form forms the' roof of a heating flue, through which pass the heating gases. These gases enter at one end of the flue and take their exit at the other, and the draft is so regulated that there will exist in this flue a minus pressure and consequently a tendency to draw into theflue the water vapors given oil from the heated charge above, through such passages or apertures as are available for that purpose. Such passages and apertures, for instance, exist between the outer edges of the, platform and the side walls of the drier structure and between the bottom of the pl'atformand the upper edges of the side walls of the draft flue.

The drier structure is provided, above the traveling platform, with a cover plate, and, consequently, as the charge gives off its water vapor in the dryin operation, the tension of the vapors aide by the draft in the fluebelow withdraws them continuously and discharges them with the spent heating gases into the drier flue stack. The opening from the flue into the stack should be in the lower part of the flue so as to assist in overcomlng any possible tendency for the 'one side wall of the compartment to the v other, these bafies having as their function the prevention of the watery vapor given off at one zone of the charge from passing on to another zone and being re-absorbed thereby instead of being taken down directly into thedraft flue.

Where filter cake from leached calcined alunite is to be dried, I prefer to load it upon the traveling platform at the hotter end of the flue, i. e., at the end where the hot ases enter the flue, and to so actuate the plat orm that the charge will move in the same direction as the hot gases. As a consequence, the high temperature of the gases acting uponthe fresh moist alumina will almost immediately bring the moisture to a point where it will' be expelled in large volume, by reason of its vapor tension, from the material and this initial volume of mois-' .ture will promptly take its exit into the flue below. A crust tends to form very quickly over the material 'on the platform. This is broken up by means of scrapers in-the shape of plow shares which project .down mto the charge to a distance which just clears the platform; These scrapers are so shaped and so arra ed as to turn the material over slowly wlthout causing dust, rolling it over in manner similar to the action of a plow in turnin over the sod of a grass field. The moisture rom the material, as hereinbefore indicated, passes down into the combustion flue, by reason of the vapor tension of the moisture aided by the draft of the In the accompanying drawings, there is illustrated a formof apparatus embodying the characteristic'features of the invention, and showin its preferred practice, although it Wlll be understood that the particular details of construction may be varied in practice, within wide limits, according to the particular material to be treated and the specific conditions of use.

In the drawings,:

Figure 1 represents (partly broken away) a vertical longitudinal section of the furnace structure;

2 represents a horizontal longitudinal section;

Fig. 3 represents 'a transverse vertical section, taken on a plane indicated by the line 3-3 of Fig.1;v

Fig. 4 represents a 4.-& of Fig. .1. v

Similar letters ofreference indicate similar parts in both views.

Referring to the drawing, B'indicates a like view on the line rails 0 which support the carryingwheels d of the movable platform. I The movable platform consists of a series of plates f, which. are linked together to form an endless-chain structure, which is distended by the sprocket wheels Y, one of which is adapted to be operated from any suitable source of power, and one of which is capable of adjustment longitudinally of the furnace structure, so as to keep the movable platform taut. In addition to the rails a the apparatus is provided with rails g arranged below the flue and which serve to support the lower strand of the plates making upthe movable platform on their return movement through the apparatus. By reference to Fig. 3, it will be noted that between the upper edge of the angle irons b and the bottom surface cfthe plates f of the movable platform there is a clearance spacewhich is provided to permit the water vapors given ofl' from the material to be drawn down into the flue B below. 7

The vertical walls of the structure in which the flue B is located are surmounted by a cover-plate L, and, below this cover plate'are arranged a series of scrapers in the form of plow shares 2', so shaped and arranged as to dip into the charge and to turn over slowly and without material production of dust the charge of leached calcined alunite, or like material, to be dried, and also to break up any crusts that may tend to form within or upon said material. A suitable hopper Z supplies the moist material to be dried to the upper surface of the movable platform, and the depth. of the layer upon the platform is determined by the adjustable gate 2 operated by the handle t, or the lik At the exit end of the movable platform is arranged the receiving pit J provided with the slide j which 'servesto seal the apparatus at that point by means of the dried material discharged upon the movable platform. At intervals along the cover L of the drier are arranged partitions. extending transversely of the entire width of the space Y 1,875,080 g &

ture given off at an advanced zone of the drier from assing rearwardly to the zones Where the rying operation'has progressed to a greater degree, and to insure that the moisture given ofl at any particular zone shall pass down into the combustion draft flue at substantially the point where the moisture is generated.

Although the invention is not limited to locating the feed hopperat the hotter end of the combustion draft flue, I nevertheless prefer to locate it at that point, in most instances, so-that the greater part of the moisture shall be given off from the material,

'per unit of travel, at the region where it is first discharged upon the traveling platform; although, as will be understood, the requirements of the heating of such materials will make it preferable vto locate the feed hopper at the colder end of the heating flue and to gradually raise'its temperature by carrying it progressively toward the hotter end thereof, the direction of travel of the moyable platform being determined accord- From the foregoing description, the mode of operation of the invention will now be clearly apparent. The leached calcined alunite, or other finely-divided material to be dried is fed upon the upper surface of the movable endless-chain platform, at a.

depth of layer determined by the adjustment of the gate 2. As the platform advances, the material encounters successively the series of plows or scrapers i which turn the material over so as to expose new surfaces to the action of the heat transmitted through the plates and to prevent whatever tendency may exist in the material to become caked or incrusted at any point throughout the charge. The moisture given off from the material passes down into the line B, by reason of the vapor tension of the moisture, assisted by the draft existing in the flue, and is continuously carried ofl through the exist passage E to the stack or other point of discharge. The speed of the movable platform, and the temperature ofthe productsof combustion or other heating medium employed in the draft flue B. are regulated to correspond to the drying eflI'ect desired. The resulting effect is that the finely-divided moist material is discharged from the end of the upper strand of plates of the movable platform dried to the degree required, and without dust loss. The

' action of the plows or scrapers insures uniformity of the drying operation and the pre vention of any substantial adhesions to the plates of the movable platform, and, inasmuch as the moisture passes 0E mainly by reason of its vapor tension, it carries practically no dust with it, so that the finelydivided material, in the dried condition required is obtained as the product of the operation in practically its entirety. So also,

because of the dustless character of the op-- eration, the drying may be carried on without discharging into the atmosphere any material amount of the finely-divided material, so that, not only from the standpoint of recoverable output, but also from the standpoint of sanitation and preservation of the surrounding locality from dust deposits the operation is correspondingly advantageous. This advantage is incident to the fact that in the drying operation, no air passes over the material, the moisture passing ofl" by reason of its vapor tension aided by the slight draft in the flue, and this result being further accompanied with a large output, because of the speed and thoroug ness with which the moisture is removed, andthe capacity of the apparatus to treat continuously large quantities of the mate rial to be dried.

As shown in Fig. 4, the apparatus is preferably provided with longitudinal guard plates w having depending edge flanges 1B. These guard plates extend from end to endin the upper compartment of the drier and have for their function to prevent any ma- I claim is:

1. A drier for finely-divided material, comprising an upper and a lower compartment, separated by a movable platform, the lower compartment constituting a flue for the passage of heating gases, an inlet below said platform for admitting the heating gases to the flue and an outlet also below -said platform for discharging the gases from the flue, and means for supplying the material to be dried to the upper side of the platform; substantially as described.

2. A drier for finely-divided material, comprising an upper and a lower compartment, separated by a movable platform, the lower compartment constituting a flue for the passage of heating gases, and communicating with the up er compartment by suitable passages fort e moisture given off in the drylng operation, and means for supplying the material to be dried to the upper side of the platform; substantially as described. u

3. drier for finely-divided material, comprising an upper and a lower compartment, separated by a movable platform, the lower compartment constituting a flue for the passage of heating gases, and communicating vv ith the upper compartment by suitscribed.

. able passages for the moisture gi'venoflt' in the drying operation, the upper compartment being provlded at intervals along its length with transverse baflies correspondingly localizing the moisture given off from the traveling charge on the platform so that it will pass down into the flue at different longitudinal zones, and means for supplying the material to bedried to the upper side of the platform; substantially as de- 4.. A drier for finely-divided material, comprising an upper and a lower compartment, separated by a movable platform, the lower compartment constituting a flue for the passage of heating gases, and the upper compartment being provided with plows or scrapers for turning over the material dur ing the drying operation-and preventing it from being incrusted upon-the platform, an inlet below said platform for admitting the heating gases to the flue and 'an outlet also below said platform for discharging the gases from the flue, and means for supplying the material to be dried to the upper side of the platform; substantially as de. scribed. i

5. A drier for finely-divided material, comprising an upper and a lower compartment, separated by a movable-platform, the lower compartment constituting a flue for the passage of heating gases, said movable platform being made up of a series of elements linked together to form an endless chain, sprocket wheels for actuating the endless chain platform, and; traction wheels therefor adapted to run upon rails located within the drier structure, and means for supplying the material to be dried to the upper side of the platform; substantially as described.

.6. A drier for finely-divided material, comprising an upper and a lower compart- -ment, separated by a movable platform, the

lower compartment constituting a flue for the passage of heating. gases, said movable 1 platform constituting an endless. chain structure, sprocket wheels for actuating the platform, traction wheels for supporting its weight, andrails upon which the traction wheels run, the rails for supporting the upper strand of the elements of the endless chain platform being located on opposite sidesof the flue compartment; substantially as described.

7. A drier for finely-divided material,

comprising an upper and a lower compartment, separated by a movable platform, the

lower, compartment constituting a flue for for supporting the lower strand of the elements of the movable platform being located in a space below the flue compartment; substantially as described.

8. A heater for finely-divided material, comprising an upper and a lower compartment supported by a movable platform, the lower compartment constituting'a flue for the passage of heating gases, the said movable platform consisting of an endless chain structure provided with traction wheels and actuated by sprocket wheels, means. for feeding the finely-divided material in an even layer to the upper side of the platform, plows or scrapers for turning over the mate-' rial during its progress through the drier means for localizing the moisture given off from the material to different zones along the length of the upper compartment, and passages connecting these zones with the flue compartment so as to permit'the moisture by reason of its expansion, aided by the draft in the flue compartment, to pass down into the flue compartment; substantially as described. I

9. In a drier for finely-divided material, comprising an up er and a lower compartment, separated y a movable platform, upon which the material to be dried is supplied, means for sealing the drier at the discharge end of the movable platform, said means consisting of a receiving pit into platform, and. a partition extending into said pit; substantially as described.

10. A drier for finely-divided material, comprising an upper and a lower compartment, separated by a movable platform, the lower compartment constituting a flue for the passage of heating gases, means for supplying the material to be dried in the upper side ofathe platform, and plates for preventing material infiltration of the combustion gases into the space'above the drying material substantially as described.

In testimony whereof I aflix my signature,

HOWARD F. CHAPPELL.

which the dried material passes from the 

